Clinical evaluation of a microsphere bead-based flow cytometry assay for the simultaneous determination of anti-thyroid peroxidase and anti-thyroglobulin antibodies

Abstract

Objectives: Multiplexing technologies based on the use of microspheres as the solid phase have opened new possibilities for the analysis of autoantibodies. As an alternative to the traditional immunoassays, it is possible to use these methods in combination with flow cytometry for simultaneous measurement of anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies.

Design and methods: We studied 127 serum samples sent to our laboratory for the quantitation of anti-TPO and anti-Tg antibodies. Clinical information was available for all of the patients studied. The samples were analyzed simultaneously for both antibodies by flow cytometry (FIDIS, BMD, France), and individually for each of the antibodies by an automated enzyme immunoassay (UniCap, Pharmacia Diagnostics, Germany).

Results: A significant association between the results was observed. The kappa agreement indices between the methods were 0.859 and 0.832 for anti-TPO and anti-Tg, respectively. Discrepant results between the two techniques were observed with no common cause. Anti-TPO and anti-Tg antibodies exhibited a non-Gaussian distribution. The areas under the ROC curves were similar for both methods used; for anti-TPO, 0.884 (Pharmacia) and 0.853 (BMD), and for anti-Tg, 0.833 (Pharmacia) and 0.837 (BMD).

Conclusion: Cytometry multiplex technology offers a true alternative to conventional immunoassays in the analysis of anti-TPO and anti-Tg antibodies.